TWI686357B - Ferrite magnet particles for filter material with shell structure - Google Patents

Abstract

An object of the present invention is to provide a ferrite magnet particle for a filter material and a filter material using the ferrite magnet particle, wherein the ferrite magnet particle for a filter material has a low apparent density and can maintain various characteristics Fill a certain volume with less weight in a controllable state. In order to achieve this, ferrite particles for filter materials having a shell structure containing Ti oxide and filter materials using the ferrite particles are used.

Description

Ferrite magnet particles for filter material with shell structure

The present invention relates to a ferrite magnet particle for a filter material, and in detail, relates to a ferrite magnet particle for a filter material and a filter material having excellent filtering ability.

The ferrite magnet particle system is used for various purposes. For example, Patent Document 1 (Japanese Patent Application: Japanese Patent Application Laid-Open No. 7-330422) describes a water-based active ceramic that uses ferrite powder or the like as an auxiliary material, and also describes a filter material used as various devices.

Although this Patent Document 1 describes the use of ferrite magnet particles as a filter material component, it is not the case as follows: focusing on various characteristics of each ferrite magnet particle, having a low apparent density, it is possible to use various types of The characteristics are maintained in a controllable state and a certain volume is filled with less weight. Moreover, the filter material described in this cited document 1 does not have sufficient filtering capacity.

On the other hand, Patent Document 2 (Japanese Patent Application: JP 2007-320847) describes an article containing a plurality of core-shell ceramic fine particles, wherein the core-shell ceramic fine particles include a core fine particle structure and a shell, The nuclear particle structure system includes a plurality of primary particles and a plurality of primary pores; and the shell system at least partially surrounds the nuclear particle structure; as an article, a film, a sensor, an electrode, and a gas collector are described.

The core-shell ceramic fine particles described in Patent Document 2 are composed of yttrium-stabilized zirconia as the core and lanthanum ferrite magnet as the shell. Since the lanthanum ferrite magnet is used as the shell, it is not as follows The situation: with a lower apparent density, it can maintain a variety of characteristics in a controllable state and fill a certain volume with less weight.

Prior technical literature

Patent Literature

[Patent Document 1] Japanese Patent Laid-Open No. 7-330422

[Patent Document 2] Japanese Patent Laid-Open No. 2007-320847

Therefore, an object of the present invention is to provide a ferrite magnet particle for a filter material and a filter material using the ferrite magnet particle, wherein the ferrite magnet particle for a filter material has a low apparent density, and can be used in a variety of The characteristics are maintained in a controllable state and a certain volume is filled with less weight.

In order to solve the above-mentioned problems, the inventors and others have devoted themselves to the study and obtained ferrite magnet particles having a shell structure containing Ti oxides, and realized that the above object was achieved, and completed the present invention. The present invention is based on these findings.

That is, the present invention provides a ferrite magnet particle for filter media, which is characterized by having a shell structure containing Ti oxide.

The ferrite magnet particles of the present invention preferably have a thickness of a portion of the shell structure of 0.5 to 10 μm.

The density of the ferrite magnet particles of the present invention is preferably lower than the density of the shell structure.

The volume average particle diameter of the ferrite magnet particles of the present invention is preferably from 10 to 100 μm.

In addition, the present invention provides a filter material using the ferrite particles.

The ferrite magnet particles of the present invention have a lower apparent density by having a shell structure containing Ti, can maintain various characteristics in a controllable state and fill a certain volume with less weight . Therefore, when the ferrite magnet particles are used as a filter agent, they can have excellent filter performance.

Fig. 1 is an electron microscope photograph (×200) of a cross section of ferrite magnet particles of the present invention, showing a method of measuring the thickness of a portion having a shell structure.

Figure 2 is a graph for image analysis from the image obtained in Figure 1.

FIG. 3 is an electron microscope photograph of FIG. 1 showing the method of measuring the outer peripheral portion of the portion having a shell structure.

Figure 4 is a graph for image analysis from the image obtained in Figure 3.

Forms for carrying out the invention

Hereinafter, the mode for carrying out the present invention will be described.

<Ferrite magnet particles of the present invention>

The ferrite magnet particles of the present invention have a shell structure (core-shell shape) containing titanium. Thereby, it has a low apparent density and can maintain various characteristics in a controllable state. In addition, the ferrite magnet particles of the present invention can fill a certain volume with a small weight of ferrite magnet particles. In addition, unless otherwise specified, the ferrite particles in the present invention mean an aggregate of ferrite particles, and in the case of particles only, refer to the ferrite particles.

Here, the case structure is a case structure in which the ferrite particles are embedded in the resin, and when the cross-sectional observation is performed using SEM, a case structure that can be visually observed must be formed on the cross-sectional SEM image. More specifically, it refers to those having a certain range of thickness and the outer peripheral portion having 80% or more of the surrounding length of the particles. It is preferable that the ratio of the surrounding length occupying the outer peripheral portion is 90% or more.

The thickness of the shell structure is preferably 0.5-10 μm, and the intended purpose can be achieved within this range. When the thickness of the outer shell structure is less than 0.5 μm, the mechanical strength of the ferrite magnet particles is weak, and because of the damage, the various powder characteristics originally possessed may not be exhibited. In particular, when used as a carrier, there is a possibility that it may break and cause a photoreceptor roller scratch. When the thickness of the case structure is greater than 10 μm, there is no change from the previous ferrite magnet particles, so even with the case structure, the desired effect may not be achieved. The thickness of the shell structure is preferably 0.5-8 μm, and 0.5-6.5 μm is the best.

The thickness of the shell structure is measured as follows. After embedding the ferrite magnet particles in the resin, as shown in Figures 1 and 2, cross-sectional observation using SEM and the resulting image can be performed Perform image processing to measure.

[Determination of shell thickness]

Here, the thickness of the shell structure of the particles is measured in accordance with the following procedure.

After embedding the ferrite magnet particles in the resin and molding, the cross section was polished using a grinder and subjected to gold vapor deposition to be used as a sample for cross section observation (for thickness measurement of the outer shell portion). The obtained sample system used JSM-6060A manufactured by JEOL Ltd., the acceleration voltage was set to 5kV, the SEM was photographed with a 200-time field of view, and the image information was imported into the image analysis software (Image-Pro PLUS) manufactured by Media Cybernetics through the interface. ) To analyze. Specifically, after adjusting the contrast of the obtained images, the brightness of the image is extracted per particle by the line profile function of the analysis software. At this time, the line contour is set to a straight line so that the approximate center of the particle passes through the horizontal direction. It exists in the peak of the obtained contour, and the peak of the corresponding shell part is sandwiched by two indicators, and the width at this time is set The thickness of the shell. In addition, the above-mentioned peak system is defined as the minimum value and the minimum value of the maximum value sandwiching the contour of the spectrum. In addition, the contrast is preferably adjusted so that the brightness of the portion (equivalent to the background) where the resin is embedded becomes 50% or less of the maximum brightness. The same operation was performed for 30 particles, and the average value was set as the thickness of the shell structure.

In addition, the ratio of the outer peripheral portion of the shell structure to the surrounding length is as described in detail below. After embedding the ferrite particles with the resin, as shown in FIGS. 3 and 4, cross-sectional observations can be made by using SEM and The obtained image is subjected to image processing and measurement.

[Measurement of the ratio of the outer circumferential direction of the shell structure]

The same image processing as described above is performed so that the line profile becomes a ring or free curve (closed curve) and the shell structure of particles per particle is set. At this time, when the maximum brightness of the contour is set to I _maximum , the minimum brightness is set to I _minimum , and the difference between the maximum brightness and the minimum brightness is set to I _△ , the range between I _minimum and less than I _minimum + I _△ × 0.2 is identified. For the part with no shell structure, I _minus + I _△ × 0.2 or more and I _max or less are recognized as the shell part. Therefore, it is possible to accumulate the spectral contour length of the luminance in which the luminance of the spectral contour length (surrounding length) obtained by the spectral contour function is I _minimum +I _△ ×0.2 or more and I _maximum or less, In addition, the ratio of the outer peripheral portion having a thickness within a certain range is calculated by dividing the contour length (peripheral length) of the spectrum line to obtain it. The same operation was performed for 30 particles, and the average value was set as the ratio of the peripheral portion to the peripheral length (=density of the peripheral portion).

[Measurement of the ratio of the porous part inside the particle]

Image processing similar to the above is performed so that the line profile becomes a straight line and is set so as to pass near the center of the particle per particle. At this time, when the maximum brightness of the contour is set to I _maximum , the minimum brightness is set to I _minimum , and the difference between the maximum brightness and the minimum brightness is set to I _△ , the range above I _minimum and less than I _minimum + I _△ × 0.2 is identified as For the parts without ferrite magnets, I _minus + I _△ × 0.2 or more and I _max or less are identified as the parts where ferrite magnets exist. Therefore, it is possible to accumulate the spectral contour length of the luminance in which the luminance of the spectral contour length (straight line) obtained by the spectral contour function is I _minimum +I _△ ×0.2 or more and I _maximum or less, and The ratio of the portion of the ferrite magnet inside the particle is calculated by dividing the profile length of the line (straight line). The same operation was performed for 30 particles and the average value was set as the density inside the particles.

The previous reduction in the apparent density of ferrite particles is mainly achieved by making the ferrite particles porous. The characteristic of this porosification is that it can be easily implemented by changing the calcination conditions during the main calcination. On the other hand, the unique pores of the porous system are uniformly generated from the surface to the inside. Therefore, when the characteristic control is performed by resin coating and resin impregnation, due to Since the resin system exists in large amounts on the surface of the particles, the influence of the coated and impregnated resin is large, and the control of the characteristics becomes very difficult.

On the other hand, according to the shape of the ferrite magnet particles of the present invention, at first glance they are conventionally existing granular particles, but they differ in the density of the particles inside the part with the shell structure (the shell part) and the particles with the porous structure For different. As a more specific feature, because the density inside the particles is low, the pore volume of the particles is large, and because the density of the outer shell portion is high, the pore size becomes large. In addition, because of its outer shell structure, it has a lower apparent density than the previous porous core. In addition, because the outside and inside of the ferrite particles are connected by local pores, although the low apparent density can maintain the surface of the ferrite particles exposed, the resin and the functional nano The suspension in which the particles are dispersed impregnates the inside of the particles, so that the outer shell part and the inner porous part can have additional functions, and novel characteristics not previously obtained by the ferrite magnet particles can be obtained.

The ferrite magnet particles of the present invention preferably contain 0.5 to 4% by weight of Mg and 3 to 20% by weight of Mn.

The ferrite magnet particles of the present invention preferably contain 47-70% by weight of Fe.

The ferrite magnet particles of the present invention preferably contain 0.5 to 4.5% by weight of Ti.

The ferrite magnet particles of the present invention contain Mg to easily adjust the magnetization. When Mg is less than 0.5% by weight, the effect of addition is small and the magnetization cannot be sufficiently controlled. When it is more than 4% by weight, the magnetization becomes low and it becomes difficult to use it for the purpose of utilizing magnetic properties.

The ferrite magnet particles of the present invention can easily adjust the magnetization and resistance even if they contain Mn. When Mn is less than 3% by weight, the effect of addition is small and the magnetization cannot be sufficiently controlled. When it is more than 20% by weight, since Mn is close to the stoichiometric ratio of the Mn ferrite magnet, the effect of the content becomes small without meaning of content. Moreover, by containing Mn, even if the oxygen concentration is constant, the magnetization can be controlled by the calcination temperature.

In addition, in terms of being able to accurately control the calcination temperature and magnetization, it is preferable to use an element containing both Mn and Mg. That is, the rough magnetization control of the ferrite magnet particles is performed by the content of Mg, and the relationship between the calcination temperature and the magnetization can be controlled in more detail by the content of Mn.

In addition, in the use of the carrier for electrophotographic developer, the ferrite particles contain Mg, so that a ferrite magnet carrier using ferrite particles and a full-color toner composed of a developer with good charge rise can be obtained. . In addition, the resistance can be increased. When the content of Mg is less than 0.5% by weight, a sufficient content effect cannot be obtained, and the image quality such as lower electrical resistance, fogging, and poor tone quality deteriorates. In addition, when used as a carrier for an electrophotographic developer, the magnetization becomes too high, which causes image defects such as hardening of the head of the magnetic brush and lines of the magnetic brush. On the other hand, when the Mg content is greater than 4% by weight, not only is the ferrite magnet carrier scattered due to low magnetization, but also when the calcination temperature is low, due to the influence of the hydroxyl group of Mg, the amount of moisture absorbed becomes large and becomes charged The reason why the environmental dependence of the electrical characteristics such as quantity and resistance deteriorates.

When the Fe content in the ferrite magnet particles of the present invention is less than 47% by weight, no shell structure is formed. On the other hand, when the Fe content is more than 70% by weight, the Mg content effect cannot be obtained and becomes substantially magnetite (magnetite) Equivalent ferrite magnet particles.

The ferrite magnet particles of the present invention preferably contain 0.5 to 4.5% by weight of Ti. Ti has the effect of lowering the calcination temperature, which not only reduces the aggregated particles, but also provides a uniform and wrinkled surface. On the other hand, when the Ti content in the ferrite magnet particles is less than 0.5% by weight, the Ti-containing effect cannot be obtained and particles having a shell structure cannot be obtained. Moreover, even if the Ti content is more than 4.5% by weight, although core-shell particles are generated, it is not easy to use them for the purpose of utilizing the magnetic properties of ferrite magnet particles, which is not good.

The difference between the Ti content of the ferrite magnet particles of the present invention and the Ti content of the ferrite magnet particles without a shell structure, that is, the difference between the Ti content near the particle surface and the inside of the particle is preferably 0.5 to 4.5% by weight.

When the difference in the Ti content is less than 0.5% by weight, since the coating amount of the composite oxide particles is small, the shell structure cannot be formed. If it is more than 4.5% by weight, the magnetization tends to be low, because it is not easy to use in applications that use the magnetic properties of ferrite magnet particles, which is not good.

The shell structure contains Ti oxides, which can be confirmed by performing elemental analysis using surveying and mapping of the aforementioned cross-sectional SEM sample using EDX. The Ti oxide here means not only TiO ₂ but also a compound that is solid-solutionized with at least one type of element constituting the ferrite particles of the matrix, such as Fe-Ti oxide and Mg-Ti oxidation Compounds, Sr-Ti oxides, Mn-Ti oxides, Mg-Fe-Ti oxides, Mg-Mn-Ti oxides, Sr-Fe-Ti oxides, Sr-Mn-Ti oxides, Sr-Mg- Ti oxide, Fe-Mn-Ti oxide, Fe-Mn-Mg-Ti oxide, Sr-Mn-Mg-Ti oxide, Sr-Fe-Mg-Ti oxide, and Sr-Fe-Mn-Ti Oxides.

The ferrite magnet particles of the present invention preferably contain 0 to 1.5% by weight of Sr. The Sr system helps to adjust the resistance and surface properties. Not only does it have the effect of maintaining high magnetization, but also the effect of improving the charging ability of ferrite magnet particles by containing it, especially in the presence of Ti, the effect is greater. When the Sr content is greater than 1.5% by weight, the residual magnetization and coercive force become high, and it is not easy to use it for applications using the soft magnetic characteristics of ferrite magnet particles.

[Content of Fe, Mg, Ti and Sr]

The contents of these Fe, Mg, Ti and Sr can be measured by the following.

It is prepared by weighing 0.2g of ferrite magnet particles (ferrite magnet carrier core material), adding 60ml of pure water, 20ml of 1N hydrochloric acid and 20ml of 1N nitric acid, heating and completely dissolving the ferrite magnet particles The aqueous solution was measured for the contents of Fe, Mg, Ti, and Sr using an ICP analyzer (ICPS-1000IV manufactured by Shimadzu Corporation).

The ferrite magnet particles of the present invention are applied 5K. 1000/4π. When the magnetic field is A/m, the magnetization measured by VSM is preferably 55~85Am ² /kg. 5K in the ferrite magnet particles. 1000/4π. When the magnetization of A/m is less than 55 Am ² /kg, it cannot be fully utilized for applications that utilize the magnetic properties of ferrite magnet particles. On the other hand, the ferrite particles are at 5K. 1000/4π. When the magnetization of A/m is greater than 85 Am ² /kg, it is not within the composition range of the ferrite magnet particles of the present invention.

[Magnetic characteristics]

The magnetic properties were measured using a vibrating sample-type magnetic gas measuring device (type: VSM-C7-10A (manufactured by Toyo Industries Co., Ltd.). The measuring sample (ferrite magnet particles) is a sample with an inner diameter of 5 mm and a height of 2 mm. The tank is installed in the above device. The measurement system increases the applied magnetic field and scans until 5K.1000/4π.A/m. Then, the applied magnetic field is reduced and a hysteresis curve is made on the recording paper. From this The data reading of the curve is 5K when the applied magnetic field. 1000/4π. A/m magnetization. In addition, the residual magnetization and coercive force are calculated in the same manner.

The ferrite magnet particles of the present invention are volume average particle diameters measured using a laser diffraction particle size distribution measuring device, preferably 10 to 100 μm, preferably 15 to 50 μm, and most preferably 20 to 50 μm. When the volume average particle diameter of the ferrite magnet particles is less than 10 μm, the low-density portion inside the ferrite magnet particles becomes relatively small, and particles with sufficiently low apparent density may not be obtained. Although core-shell particles can be produced even if the volume average particle diameter of the ferrite magnet particles is greater than 100 μm, it means that the voids are reduced when the ferrite magnet particles are closely packed in a certain volume, preferably 100 μm or less.

[Volume average particle size]

The volume average particle diameter is measured using a laser diffraction scattering method. As a device, a Microtrac particle size analyzer (Model 9320-X100) manufactured by Nikkiso Co., Ltd. was used. The refractive index was set to 2.42 and the measurement was performed in an environment of 25±5°C and humidity of 55±15%. Here, the so-called volume average particle diameter (median particle diameter) refers to the cumulative 50% particle diameter in the volume distribution mode and expressed as the under sieve. Water is used as the dispersion medium.

The ferrite magnet particles of the present invention preferably have a BET specific surface area of 0.2 to 1 m ² /g, more preferably 0.2 to 0.85 m ² /g.

When the BET specific surface area is less than the above range, it means that the outer shell structure is not sufficiently formed and the particles are also tightly packed inside the particles, which is not good. When the BET specific surface area is larger than the above range, it also means that a shell structure cannot be formed and porous ferrite particles can be obtained. In addition, when measuring the BET specific surface area, the measurement result may be affected by the moisture of the surface of the ferrite particles, which is the measurement sample. Treatment before removing the water is better.

[BET specific surface area]

For the measurement of the BET specific surface area, a specific surface area measuring device (model: Macsorb HM model-1208 (manufactured by MOUNTECH)) was used. Add about 5 to 7 g of the measurement sample to the standard sample tank for the specific surface area measurement device, accurately weigh it using a precision balance, and install the sample (ferrite particles) in the measurement port and start the measurement. The measurement system is performed using the one-point method, and the weight of the sample is input at the end of the measurement to automatically calculate the BET specific surface area. In addition, as pre-measurement pre-measurement, about 20 g of the measurement sample was dispensed into the medicine wrapper, degassed to -0.1 MPa using a vacuum dryer, and after confirming that the degree of vacuum reached -0.1 MPa or less, heated at 200°C 2 hour.

Environment: temperature; 10~30℃, humidity; relative humidity is 20~80% without condensation

The ferrite magnet particles of the present invention have a resistance of 50V applied at 6.5mmGap, preferably 5×10 ⁷ to 1×10 ¹¹ Ω.

When the resistance of the ferrite particles with a voltage of 50V applied at 6.5mmGap is less than 5×10 ⁷ Ω, it means that the ferrite magnet composition becomes close to magnetite, or the amount of Ti added is small and the shell structure cannot be sufficiently formed. When the resistance of the ferrite magnet particles is higher than 1×10 ¹¹ Ω, the Ti content on the surface of the ferrite magnet particles becomes too much and there is a possibility that the magnetization will be greatly reduced.

[resistance]

This resistance is measured as follows.

A non-magnetic parallel plate electrode (10 mm×40 mm) was made to face with an interval of 6.5 mm between the electrodes, and 200 mg of a sample (ferrite particles) was weighed and filled in between. By contacting the magnet (surface magnetic flux density: 1500 Gauss), The area of the magnet of the electrode: 10mm×30mm) is attached to the parallel flat electrode, keeping the sample between the electrodes and applying voltages of 50V, 100V, 250V, 500V and 1000V, using an insulation resistance meter (SM-8210, East Asia DKK (share)) Measure) the resistance when the voltage is applied.

Preferably, the ferrite magnet particles have a pore volume of 0.06 to 0.2 ml/g (60 to 200 μl/g) and a peak pore diameter of 0.7 to 2 μm.

When the pore volume of the ferrite particles is less than 0.06 ml/g (60 μl/g), it means that the pores inside the particles are smaller and do not become particles with a lower apparent density. In addition, when the pore volume of the ferrite magnet particles is greater than 0.2 ml/g (200 μl/g), it means that the apparent density is too low. As a particle of magnetic powder, its magnetic force decreases and the magnetic force of the ferrite magnet particles is used. There is a possibility that the use of the characteristics may cause defects.

When the peak pore diameter of the ferrite magnet particles is greater than 2 μm, it means that the particles do not become particles with a low apparent density, and sufficient characteristics cannot be obtained for the purpose of using the low-density portion inside the ferrite magnet particles. In addition, when the peak pore diameter of the ferrite magnet particles is less than 0.7 μm, there is a high possibility that they become porous ferrite magnet particles without a shell structure, and the use for the function of dividing the inside and outside of the ferrite magnet particles changes. The possibility of difficulty.

In this manner, when the pore volume and the peak pore diameter are in the above-mentioned range, ferrite magnet particles that can be appropriately reduced in weight without the above-mentioned various defects can be obtained.

[Pore diameter and pore volume of ferrite magnet particles]

The pore diameter and pore volume of the ferrite magnet particles are measured as follows. That is, it was measured using mercury porosimeter Pascal 140 and Pascal 240 (manufactured by Thermo Fisher Scientific). Thermal expansion meter (dilatometer) uses CD3P (for powder), and the sample is placed in a commercially available gelatin capsule with multiple holes excavated and placed in a thermal expansion meter. After degassing with Pascal 140, fill with mercury and measure the low pressure area (0~400kPa) as the first operation (1st Run). Next, perform degassing and measure the low pressure area (0~400kPa) again as the second operation (2nd Run). After the second operation, the weight was measured with the thermal dilatometer, mercury, capsule, and sample. Next, Pascal 240 was used to measure the high-pressure region (0.1 MPa to 200 MPa). The pore volume, pore size distribution, and peak pore size of the ferrite particles are determined based on the amount of mercury intrusion measured in the high-pressure section. In addition, when calculating the pore diameter, the surface tension of mercury was calculated to be 480 dyn/cm and the contact angle was 141.3°.

<The manufacturing method of the ferrite magnet particle of this invention>

Next, the method for producing ferrite magnet particles of the present invention will be described.

The method for producing ferrite magnet particles of the present invention can be performed as follows, for example.

(Preparation of particles for ferrite core material)

After each compound of Fe, Mn, Mg, and compounds such as Sr, Ti, etc. as needed is pulverized, mixed, and pre-calcined, it is pulverized using a rod mill and is set as a ferrite magnet pre-calcined powder.

An example of a preferred composition of the ferrite magnet pre-calcined powder is that Fe is 45 to 68% by weight, Mg is 0.5 to 4% by weight, Mn is 3 to 22% by weight, Ti is 0.25 to 6% by weight, and Sr is 0 to 2% by weight.

By satisfying the above composition range of the ferrite magnet pre-calcined powder and by coating the Ti compound and then calcining, it is possible to obtain various characteristics necessary as ferrite magnet particles according to the application.

After pre-calcining the above ferrite magnet powder, adding water and optionally dispersing agent, binder, etc. as a slurry and adjusting the viscosity, use a spray dryer to granulate and granulate, and then carry out the debinding agent treatment. The ferrite particles before coating were obtained. The debonding agent treatment is carried out at 600~1000℃.

The slurry particle diameter D _{50 of the} above slurry is preferably 0.5 to 4.5 μm. By setting the particle diameter of the slurry within the above range, ferrite magnet particles having a desired BET specific surface area can be obtained. When the particle size D _{50 of the} slurry is less than 0.5 μm, the specific surface area of the pre-calcined ferrite magnet powder becomes too large. When the TiO ₂ particles are coated and then the ferrite magnet particles are calcined, excessive calcination is not possible. Ferrite magnet particles having the required BET specific surface area are obtained. When it is larger than 4.5 μm, even if it is coated with TiO ₂ particles for coating and calcined, there is a possibility that the shell structure cannot be sufficiently formed and cannot be required ferrite magnet particles.

In order to make the slurry particle size into the above range, the crushing time is controlled when the slurry for granulation is prepared, or the crushing medium is selected in such a manner as the target slurry particle size and particle size distribution, or a wet cyclone is used Instead, the raw material particles present in the slurry may be classified. Although when using a wet cyclone, the solid content of the slurry after classification is different, it is necessary to adjust the solid content again, but it can be used in combination with the control of the pulverization time because it can become the target slurry particle size in a short time.

The volume average particle diameter of the TiO ₂ particles for coating is preferably 0.05 to 3 μm. When it is less than 0.05 μm, when the fine particles are adhered to the surface of the ferrite particles before coating, the coated particles tend to become aggregates, and even if they are coated on the surface of the former ferrite particles with the required coating amount, they are likely to be generated in the coating layer There is a possibility that the housing structure cannot be formed unevenly and partially. When it is greater than 3 μm, it is not easy to uniformly adhere to the ferrite particles before coating, and there is a possibility that the outer shell structure cannot be partially generated in the ferrite particles.

Although it also depends on the volume average particle size of the TiO ₂ particles for coating, the TiO ₂ particles for coating are preferably 0.8 to 7 wt% compared to the ferrite particles before coating. When it is less than 0.8% by weight, sufficient resistance cannot be obtained after the actual calcination. When it is more than 7 wt%, the ferrite magnet-coated particles that have not adhered to the ferrite magnet particles before the coating agglomerate with each other and may form low-magnetization particles are used for the purpose of utilizing the magnetic properties of the ferrite magnet particles. Possibility of bad causes.

(Modulation of ferrite magnet particles)

The TiO ₂ particles for coating were added to the ferrite particles before coating obtained as described above, and mixed using a mixing mill as a raw material for ferrite particles. The raw material for the ferrite magnet particles is subjected to the calcination at 850 to 1230°C in an inert environment or a weakly oxidizing environment, such as a nitrogen environment and a mixed gas environment of nitrogen and oxygen with an oxygen concentration of 3% by volume or less.

Subsequently, the calcined product was crushed and classified to obtain ferrite magnet particles. As the classification method, the existing air classification, screen filtration method, sedimentation method, etc. are used to adjust the particle size to a desired particle size. In the case of dry recycling, it is also possible to use a cyclone or the like for recycling.

By doing so, the ferrite magnet particles of the present invention having the above-mentioned characteristics can be obtained.

In order to obtain easy dispersibility on the surface of the attached coating TiO ₂ particles in the ferrite magnet particles of the present invention, a surface treatment for imparting charge may be performed. By performing the surface treatment to impart charging, the aggregation between the particles is reduced, and the coated TiO ₂ particles before the main calcination become easy to adhere. In addition, by using a surface treatment agent having a polarity opposite to the polarity of the ferrite particles before coating, it is possible to obtain the effect of preventing detachment of the coating TiO ₂ particles attached to the ferrite particles before coating before the main calcination.

After attaching the coating TiO ₂ particles to the surface of the pre-coating ferrite magnet particles before the main calcination, the method of performing the main calcination is as described above, using the coating TiO ₂ particles that are not subjected to the dry pre-treatment to make them adhere When the surface of the pre-coated ferrite particles before the main calcination, the coating TiO ₂ particles attached to them are excessively aggregated and it is not easy to adhere to the pre-coated ferrite particles, or they are adhered in the form of larger aggregates to cause the composition The deviation is large, and the characteristics of the ferrite magnet particles obtained after the actual calcination are inferior.

The surface of the TiO ₂ particles for coating the ferrite particles before the coating before the main calcination is coated by the wet method, because the liquid as the solvent must be removed together with the raw materials for the ferrite particles after the surface coating, In terms of steps, the system becomes large-scale, so the cost increases. By coating the TiO ₂ particles for coating on the ferrite particles before coating in a dry manner, only the surface treatment of the TiO ₂ particles for coating may be performed, and the advantage is that it can be easily performed and the cost increase is small.

<Filter material of the present invention>

By using the ferrite magnet particles of the present invention as a filter, it has excellent filtering performance.

Hereinafter, the present invention will be specifically described based on examples and the like.

[Example 1]

[Modulation of ferrite magnet particles]

Weigh to be 100 mol Fe ₂ O ₃ , 10 mol MgCO ₃ , 13.3 mol Mn ₃ O ₄ and 1 mol SrCO ₃ , and add 1.35% by weight of carbon black as a reducing agent relative to the weight of the raw material After mixing and pulverizing, the former is pelletized using a roller compactor (Roller Compactor). In a rotary calciner, the obtained pellets were pre-calcined under a nitrogen atmosphere at 980°C and an oxygen concentration of 0% by volume. The pulverized product using a rod mill is set as the pre-calcined powder for the ferrite core material.

The ferrite core material was pulverized with a pre-calcined powder using a wet bead mill for 1 hour, and PVA was added as a binder component so as to be 1% by weight relative to the solid content of the slurry, and the viscosity of the slurry became 2~ The polycarboxylic acid-based dispersant is added in a 3-poise manner. At this time, the slurry particle diameter D ₅₀ was 3.259 μm.

The pulverized slurry thus obtained was granulated and dried using a spray dryer, and subjected to a debinding agent treatment at 850°C using a rotary kiln (Rotary Kiln) under a nitrogen atmosphere at an oxygen concentration of 0% by volume to obtain ferrite. Particles for magnet core material.

To the above ferrite core material particles, 4% by weight of the coating TiO ₂ particles were added, and the mixture was stirred with a mixing mill for 10 minutes. The obtained mixture was used as a raw material for ferrite magnet particles to disaggregate the aggregate using an 80-mesh vibrating screen.

The raw materials for the ferrite magnet particles obtained above were subjected to main calcination using an electric furnace under a nitrogen atmosphere at an oxygen concentration of 0% by volume at 1010° C. for 4 hours. Subsequently, it is pulverized and classified to obtain ferrite magnet particles.

[Example 2]

The same method as in Example 1 was used except that it was weighed as 100 mol Fe ₂ O ₃ , 5 mol MgCO ₃ , 26.6 mol Mn ₃ O _4, and 0 mol SrCO ₃ as ferrite magnet raw materials. Ferrite magnet particles are obtained.

[Example 3]

The same method as in Example 1 was used except that it was weighed as 100 mol Fe ₂ O ₃ , 20 mol MgCO ₃ , 6.65 mol Mn ₃ O ₄ and 0 mol SrCO ₃ as ferrite magnet raw materials. Ferrite magnet particles are obtained.

[Example 4]

The same method as in Example 1 was used except that it was weighed as 100 mol Fe ₂ O ₃ , 5 mol MgCO ₃ , 5 mol Mn ₃ O _4, and 0 mol SrCO ₃ as ferrite magnet raw materials. Ferrite magnet particles are obtained.

[Example 5]

The same method as in Example 1 was used except that the ferrite magnet raw material was weighed so as to be 100 mol Fe ₂ O ₃ , 20 mol MgCO ₃ , 26.6 mol Mn ₃ O ₄ and 0 mol SrCO ₃ . Ferrite magnet particles are obtained.

[Example 6]

The ferrite magnet particles were obtained in the same manner as in Example 1, except that SrCO _{3 was} set to 0 moles, and 2.5% by weight of the coating TiO ₂ particles were added to the ferrite core material particles.

[Example 7]

The ferrite magnet particles were obtained in the same manner as in Example 1, except that SrCO _{3 was} set to 0 moles and 5 wt% of the coating TiO ₂ particles were added to the ferrite core material particles.

[Example 8]

The ferrite magnet particles were obtained in the same manner as in Example 6, except that the main calcination temperature was 950°C.

[Example 9]

The ferrite magnet particles were obtained in the same manner as in Example 6, except that the main calcination temperature was 1050°C.

[Comparative Example 1]

The ferrite magnet particles were obtained in the same manner as in Example 1, except that SrCO _{3 was} set to 0 moles and the main calcination temperature was set to 920°C.

[Comparative Example 2]

The ferrite magnet particles were obtained in the same manner as in Example 1, except that SrCO _{3 was} set to 0 moles and no TiO ₂ particles for coating were added to the particles for the ferrite core material.

[Comparative Example 3]

The ferrite magnet particles were obtained in the same manner as in Example 1, except that SrCO _{3 was} set to 0 moles and the main calcination temperature was set to 1165°C.

The ratio of the ferrite particles used in Examples 1 to 9 and Comparative Examples 1 to 3 (molar ratio of raw material addition), carbon content, pre-calcination conditions (pre-calcination temperature and pre-calcination environment) Granulation conditions (slurry particle size and PVA added weight), debinding agent treatment conditions (treatment temperature and treatment environment), TiO ₂ mixing conditions (addition amount and mixing conditions), and formal calcination conditions (formal calcination temperature and formal calcination environment) As shown in Table 1, the composition, magnetic properties (magnetization, residual magnetization, and coercive force) of the obtained ferrite magnet particles and the shape of the ferrite magnet particles (cross-sectional shape, the portion with the shell structure occupying the surrounding length ratio, have Table 2 shows the thickness of the part of the shell structure and the occupancy ratio of the ferrite particles inside the particles). Furthermore, the powder characteristics (BET specific surface area, average particle diameter, apparent density, true specific gravity, pore volume and peak pore diameter) of the ferrite particles of Examples 1 to 9 and Comparative Examples 1 to 3 and 6.5 mm Gap The bridge resistance (50V, 100V, 250V, 500V and 1000V) is shown in Table 3. Each measurement method is as described above.

As shown in Table 2, any of the ferrite magnet particles of Examples 1 to 9 can be obtained with a shell structure.

On the other hand, although the calcination temperature of the ferrite magnet particles in Comparative Example 1 is low and a porous structure is generated, ferrite magnet particles having a shell structure cannot be obtained.

The ferrite magnet particle system of Comparative Example 2 does not add TiO ₂ particles for coating. The ferrite magnet particles of Comparative Example 2 cannot be ferrite magnet particles having a shell structure.

The ferrite magnet particles of Comparative Example 3 are high in calcination temperature and cannot be ferrite magnet particles having a shell structure.

[Example 10]

A stainless steel mesh was processed into a circle so as to have a diameter of 125 mm, and instead of filter paper, a suction filter (Nutsche) funnel with an inner diameter of 125 mm was installed. The suction filter funnel was installed on a filter bottle. Each 500 g of ferrite particles obtained in Example 1 were prepared and put on a suction funnel so as to become flat. While suctioning with an aspirator, inject 500cc of a methanol dispersion of titanium oxide with a 50% transmittance and an average particle size of 0.13μm from above, and draw until the filtrate does not trickle down again. The transmittance of the liquid was used to evaluate the filtering ability of the ferrite powder. Subsequently, the filtrate accumulated in the filter bottle was discarded, a suction funnel holding ferrite particles was attached to the filter bottle, methanol was injected from above to perform the second filtration, and the filtrate was measured in the same manner as the first The transmittance.

[Comparative Example 4]

In addition to using the ferrite magnet particles obtained in Comparative Example 1 instead of Example 1 Except for the obtained ferrite magnet particles, the transmittance of the filtrate was evaluated in the same manner as in Example 10.

[Comparative Example 5]

The transmittance of the filtrate was evaluated in the same manner as in Example 10 except that the ferrite magnet particles obtained in Comparative Example 2 were used instead of the ferrite magnet particles obtained in Example 1.

[Comparative Example 6]

The transmittance of the filtrate was evaluated in the same manner as in Example 10 except that the ferrite magnet particles obtained in Comparative Example 3 were used instead of the ferrite magnet particles obtained in Example 1.

Table 4 shows the specific surface area and transmittance of the ferrite magnet particles used in Example 10 and Comparative Examples 4 to 6 using the air permeation method. The specific surface area and transmittance of the air permeation method in Table 4 are measured according to the following.

[Determination of specific surface area of ferrite magnet particles using air permeation method]

The measurement of the specific surface area using the air permeation method is to measure and calculate the specific surface area from the time required for the air to pass through the ferrite particles filled in the sample tank. This value is a suitable measurement method for measuring the area limited to the surface portion of the ferrite magnet particles. The measurement method is based on JIS R 5201 (Physical Test Method for Cement).

[Transmittance]

For the transmittance, a spectrophotometer UV-18000 manufactured by Shimadzu Corporation was used. When the wavelength used in the measurement was set to 500 nm and the transmittance of methanol was set to 100, the filtering effect of the ferrite magnet particles was evaluated.

As shown in Table 4, in the first filtration, the transmittance in Example 10 becomes high, and it can be confirmed that the ferrite particles have a filtering effect. In Comparative Examples 4 to 6, although the transmittance has a certain increase and also has a filtering effect, the titanium oxide particles present on the surface of the ferrite magnet particles are separated from the ferrite magnet particles during the second filtration, compared with In Example 10, it was a poor result.

Industrial possibilities

The ferrite magnet particles of the present invention have a low apparent density by having a shell structure, can maintain various characteristics in a controllable state, and fill a certain volume with less weight. Therefore, by using the ferrite particles as a filter, the filtering ability is greatly improved.

Claims (5)

A ferrite magnet particle for a filter medium, which is characterized by having a shell structure containing Ti oxide and a porous structure inside the particle. The ferrite particles for filter media as described in item 1 of the patent application range, wherein the thickness of the portion having the above-mentioned shell structure is 0.5 to 10 μm. The ferrite magnet particles for filter media as described in item 1 or 2 of the patent application range, wherein the density inside the particles is lower than the density of the above-mentioned shell structure. The ferrite magnet particles for filter media as described in item 1 of the patent application range, in which the volume average particle diameter is 10 to 100 μm. A filter material that uses ferrite magnet particles as described in any of items 1 to 4 of the patent application.

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